Rotary hook construction



j Aug- 10, 1955 J. N. covERT ETAL 3,199,480

ROTARY HOOK CONSTRUCTION 2 Sheets-Sheet 1 Filed OCT.. 19, 1962 Allg 10, 1955 J. N. COVER-r ETAL 3,199,480

ROTARY HOOK CONSTRUCTION 2 Sheeos-SheefI 2- F'iled OCL. 19, 1962 FIGS.

United States Patent O 3,199,486 RTARY Hl CNSTRUCTHN John N. Covert, Lombard, lil., and Paul D. Pryor, Williamsport, Pa., assignors to Union Special Machine Company, Chicago, lli., a corporation of Iliinois Filed Get. 19, 1962, Ser. No. 231,773 8 Claims. (Cl. 1lb-123i.)

This invention relates to improvements in the construction of rotary hooks employed in lockstitch sewing machines adapted for high speed operation of the character desired in machines intended for industrial use. In this category are machines of the type disclosed in the U.S. patent to Covert, et al., No. 2,977,910, granted April 4, 1961.

In the operation of machines of the character indicated, there has been found a great tendency toward the accumulation of lint within the rotary hook in the region in which the needle of the sewing machine passes through an opening in the rotary hook structure to carry thev needle thread to a point within the body of the rotary hook and in the path of the loop seizing beak of the hook. Accumulation of such lint has been found to interfere with the proper formation of a loop in the needle thread as the needle is being withdrawn from the interior of the hook. Frequently this has resulted in the skipping of stitches, because the beak of the hook has not been able to pass properly through a loop in the needle thread. The desired loop has not been properly formed as a result of the interference created by the accumulated lint. Occasionally the pressure of the lint on the needle thread has been such as to bring about breakage of the latter.

One of the primary purposes of the present invention is to provide a simple expedient for the periodic removal of lint from the passage mentioned above. This has been achieved through the provision on the bobbin case of -a suitable outward projection which serves as a lint removing plow each time that the bobbin case is removed for the purpose ol' introducing a new bobbin into the case. During normal sewing machine operations the bobbin case is removed for replacement of the empty bobbin about every 7-12 minutes, depending upon the length of the seams being produced and the complexity of the sewing operations. lt will thus be seen that the plow of the present invention will be effective every 7-12 minutes to remove any lint which has accumulated within that brief interval in the region in which it is likely to cause trouble.

A further important feature of the present invention is the Aformation of the lint removing plow in such a way that a portion of it serves as a needle guard, which replaces the needle guard conventionally provided heretofore on the bobbin case holder. An important advantage `of this aspect of the invention is that the needle guard surface is provided in a location which is closer to the axis of the rotary hook structure, and therefore closer to the innermost position to which the point of the needle is carried in the course of the Operation of the machine. By virtue of this inward location of the needle guard, it has a far less tendency to interfere with the proper formation of a loop in the needle thread as the needle starts its upawrd movement. This again minimizes the danger of lskipping stitches. As will be understood, the purpose of the needle guard is to make certain that the needle itself is disposed outwardly of the path of the beak of the hook. That purpose is more effectively achieved by the preferred construction of the present invention than in prior art structures.

A further advantage of having the needle guard carried by the bobbin case is that this makes it readily removable and therefore conveniently visible for inspection and repair or replacement purposes. lt is desirable to inspect ICC the needle guard from time to time to determine whether it has been nicked by the tip of the needle. lf inspection shows that this has happened, the knicks or burrs may be readily removed by a simple polishing or bufng operation. The interval during which the machine may be left idle for this purpose, with the hook construction of the present invention, is quite short. In fact, if the operator does not wish to stop operation of the machine during the brief interval required to buff the combined plow and needle guard upon one of the frequent removals of the bobbin case, a spare bobbin case may be used and the sewing operation continued with substantially no interruption. In contrast to this, conventional rotary hooks, having the needle guard on the bobbin case holder, require the throat plate of the machine to be removed in order to enable reasonable inspection of the needle guard. lf the guard is found to be knicked or damaged, the entire hook must be removed from the machine and disassembled to enable the necessary repair job to be performed. This obviously requires a great deal of time during which the machine must be kept out of operation.

A further feature of the invention, which is directly related to and combined with the provision of the lint plow and needle guard on the bobbin case, is the provision of a hook retaining linger which is fixed to the frame of the machine, this finger extending from a horizontally disposed retaining arm that has a curved under surface which provides clearance for the plow and guard as the bobbin case is inserted and removed.

Still another feature of the invention is the provision of a clearance cut in the outer portion of the wall of the bobbin case holder to rather snugly receive the needle guard and lint plow on the bobbin case. The arrangement as a whole is such that the usual proof pins provided on the inner wall of a conventional bobbin case holder, in its upper portion, may be eliminated. Such proof pins are employed in conventional bobbin case holders to guide the bobbin case into proper position to enable the retaining latch arm to function properly. This function is achieved in accordance with the present invention, by the cooperation of the clearance cut in the bobbin case holder with the lint plow and needle guard on the bobbin case.

Other objects, features and advantages of the invention will appear from the detailed description of a preferred embodiment which will now be given in conjunction with the accompanying drawings, in which:

FIG. 1 is a view partly in vertical section and partly in elevation, showing the relationship between the upper portion of the rotary hook assembly, the throat plate of the machine and the arm which carries the finger that cooperates with the bobbin case holder to retain the latter against any substantial rotation;

FlG. 2 is a plan view of the improved rotary hook, a.

portion of the shaft on which it is mounted and the member carrying the retaining linger;

FlG. 3 is a vertical sectional view taken along the line 3-'3 of FG. l, and shows the case and its retainer and the relationship between the various parts as the needle is moved upwardly to provide the desired loop in the needle thread;

FIG. 4 is a perspective view of the bobbin case of the invention;

FIG. 5 is a top plan view of the bobbin case holder with the bobbin case therein, constructed in accordance with the invention; and

FIG. 6 is a face view of the bobbin case holder.

The rotary hook of the present invention may be use-rl in any of a variety of different forms of horizontal hook lockstitch machines. Typical of these are that shown in the patent to Kessler, No. 2,085,699, granted lune 29, 1937, and the patent to Hale No. 2,762,325, granted Sept.

`into the interior of the bobbin case.

1l, 1956. The rotary hooks employed may be of the general form shown in those patents or in the patent to Covert et al., No. 2,694,373, granted Nov. 16, 1954, or in the patent to Attwood No. 2,941,488, granted lune 2l, 1960. However, it will be understood that the construe* tions of the rotary hook assembly disclosed in those patents are modied in accordance with the present invention to provide the improved features discussed above.

Referring now to the drawings, there is shown in FlG. 2 the rotary component l@ ot the rotary hook assembly, this rotary component being secured to a shaft ll which is driven at twice the angular speed of the main drive shaft of the machine. Rotary component l@ has a beak ltlla adapted to pass through a loop of the needle thread at an appropriate time during each two revolutions of member l0. As in conventional hook constructions, member lill has two readily removable elements ltlb and lille secured by screws to the body of member Element lob, when detached from the main body of the rotary component, permits the introduction and removal from the assembly of a bobbin case retainer' or basket l2. Extending outwardly from the center of the bottom of the basket is a post 12a which serves to receive a tubular, central member lof of the bobbin case to be described. Adjacent its outer end, the post lf/Za has an annular groove providing a reduced diameter portion ille with which suitable locking means carried by the bobbin case cooperates. The bobbin case basket has a rib lZc extending outwardly around the greater portion of its circumference, this rib cooperating with a groove within the rotary component l@ to retain the parts l@ and i?. against any substantial axial movement while permitting free rotation of member lli about member F.2d. ln its upper portion, the member l2 is provided with a radially extending groove ld adapted to cooperate with a retainer member i3. The latter is secured by screws 3.4 to the undersuriace of the top l5 of the base of the machine. Adjacent the groove 12d, member 13 is provided with a laterally and upwardly extending linger or projection l3b adapted to fit into the groove 12d in a manner permitting only slight rotation of the bobbin case basket. lt will be understood that when the machine is in operation the bobbin case basket l2 will be urged frictionally in a counterclockwise direction as the rotary con1- ponent l@ is driven in that direction. At an appropriate time in the cycle of operation of the machine, suitable means comes into play to turn the bobbin case basket slightly in a clockwise direction to enable the passage of needle thread between cooperating surfaces on the lett side wall of the groove lita' (FIG. l) and on the left side of the linger "13b, The undersurface of member 13 is cut away, preferably along an arc, as indicated at 13a. This permits ready removal of the special bobbin case to be described.

in FG. 4- there is best shown the improved form of bobbin case .le which is adapted to be readily inserted into and removed from the bobbin case basket to enable the replacement of a new bobbin carrying a full supply of thread for the bobbin that has become exhausted. ln accordance with conventional practice the bobbin case is provided with a spring urged lever 16a which, upon outward movement of its outer end, serves to enable removal of the bobbin case from the bobbin case basket. The means for this purpose is well known in the art and need not be described in further detail. Suce it to say that it involves a slide g having an opening provided with shoulders adapted to cooperate with the reduced diameter portion 12e of post 12in.

Extending radially outwardly from a small portion of the circumference of the cylindrical body of the bobbin case is a projection lob. The latter extends over an arc in the region of the groove 12d of the bobbin case basket which, as will be explained, is the region in which the needle of the sewing machine is reciprocated and carried he forward face lloc of the projection lfb is inclined at a suitable angle to the vertical, as best shown in FllG. 3. This, as will be explained, provides a highly desirable needle guard. lnclined surface lds, at its lower end, merges into a radially extending surface ldd at the inner end of a cutaway portion lie (FIG. 4) at the front of the bobbin case. The projection llh may be formed integral with the wall of the bobbin case or it may be formed as a separate element which is welded or otherwise secured to the main wall of the bobbin case. he integral form is shown in PEG. 3, while the separate forni is shown in FlG. 4, wherein the radially extending arcuate edge ldd is provided by the cylindrical body of the bobbin case. shown in FlG. 4, the cylindrical body of the bobbin case is not interrupted or cut away completely from the outer to the inner end thereof, as is conventional, in the region aligned with the projection lh of the present invention. lt is cut away only slightly in the region forwardly of the projection This cutaway portion of the prior art bobbin cases is provided to facilitate the proper introduction o the latter into the bobbin case basket, and the edges ot the main body provided by the conventional cutaway cooperate with nubs or proof pins extending outwardly from the inner wail or bottom of the bobbin case basket to insure retention of the bobbin case in a definitely fixed relation to the bobbin case basket. By the present invention, the projection leb serves this purpose, and. the main cylindrical body ot the bobbin case is made stronger and more resistant to deformation at its inner, open end than in the prior art constructions hav- `ing the cutaway portion mentioned above.

A reciprocatory needle i7 (PLUS. l and 3) is adapted to be driven in the conventional manner to move vertically by suitable connections from the main drive shaft of the machine. The pointed end of the needle is moved from a position above a throat plate `lt; carried by the work supporting surface of the base of the machine to the point indicated at l (FIG. l) which is well within the interior of the bobbin case basket. An opening ida is provided through the throat plate for the passage of the needle as it is reciprocated. Other openings are provided in the throat plate l, and it will be understood that these are for the upward passage of rfeed dogs which are provided to advance the work in the course of a stitching operation. The bobbin case basket .l2 is provided with an opening lZf (FIG. 5) which extends to the inner face of a radially projecting flange 12g of the bobbin case basket. The needle passes downwardly between this llange and the projection i622 on the bobbin case. In the event that the lower end of the needle is deflected toward the right (PlG. 3), by the movement of the work being stitched, or the like, the point of the needle will strike the inclined surface les of projection lieb and will be deliected by this surface toward the right so as to enable it to pass downwardly to position ll (PEG. 1). lt -is important that when the needle is in its lowermost position it is out of the path of the loop seizing beak ida. and is slightly to the left of said path (FlG. 3). ln that ligure there are shown two layers of fabric l@ which are being subjected to the seaming operation and are advanced across the surace or" the throat plate. The needle i7 carries a thread Ztl which is caused to form a loop as the needle is moved upwardly to a slight extent from its lowermost position. t is important that this loop open out automatically at this stage of the sewing operation so that the loop seizing beak we of the rotary component lll will enter .and pick up the loop 2da. From -l-"lG, 3 it is appar ent that the location ot the needle guard surface 16e at a relatively low position beneath the path of movement of the beak .litio is important to the insurance of the formation of a proper loop 2da. Provision of the needle guard surface on the bobbin case, rather than on the bobbin case basket or some other part of the machine, serves Asv ing 16e in the bobbin case lead toward the accumulation in this area of a certain amount of lint that is forced downwardly from the fabric by the needle. With rotary hook constructions of the prior art such accumulation of lint over a long period of time has been found to lead to difliculties of the character set forth at the beginning of this specification. The accumulation of such an excessive amount of lint is prevented by the present invention through the plow action of the projection lob of the 'bobbin case upon the removal of the latter to insert a new bobbin. It will -be understood that the bobbin has a central opening therethrough which is received by the Ihollow stern 16f of the bobbin case. As has been explained, it is necessary to remove the bobbin case from the bobbin case basket about every 7 to 12 minutes of sewing time in order to rep-lace an exhausted bobbin by .a bobbin having a new `supply of thread for the hook. Such frequent removal of the bobbin case has been found to eliminate any objectionable accumulation of lint within the openings mentioned. Also as has been explained earlier, the provision of the needle guard on the bobbin case rather than on some other part of the structure, makes the needle guard Ireadily and frequently available for inspection to determine whether it has been seriously knicked yand therefore requires buing or the like to restore a smooth surface. This greatly reduces the length of time lduring which a machine must be left out of operation for the inspection of the needle guard and the correction of any damage which may have been done to it. In fact the operator may be provided with a spare bobbin case, so that if knicking of the needle guard surface is noted in the course of changing bobbins, the spare bobbin case may be substituted for the one removed from the machine so that no loss of time will be encountered.

W-hile a preferred embodiment of the invention has been described in some detail, it Will be understood that varitous modifications may be made without departing from the principles and scope of the present invention.

What is claimed is:

1. In .a lockstitch sewing machine having a drive shaft and a reciprocatory needle and a rotary hook driven from said shaft for rotation about a horizontal axis, said rotary hook having a rotary loop seizing member, a bobbin case retainer within Isaid member, means for retaining said bobbin case retainer against rotation with said loop seizing member, a bobbin case mounted within said retainer and axially removable therefrom, said bobbin case having means extending outwardly therefrom in the direction of reciprocation of said needle and inwardly of the pat-h of rcciprocation of the needle, and means for retaining a bobbin AWithin said case for rotation of said bobbin Within said case, said bobbin case being slidable into and out of sai-d retainer for the replacement of the bobbin therein, and said means extending outwardly from the bobbin case cooperating with said bobbin case retainer for removing therefrom, upon each removal of said bobbin case, lint which has accumulated within said retainer during the preceding operation of the machine.

2. A rotary hook for a lockstitch machine which comprises a rotary component mounted rotation about a horizontal axis and having a loop seizing break, a reciprocatory needle for presenting a loop of thread to said loop seizing beak, a bobbin case retainer Within said rotary component and about Which said component is rotated, a bobbin case mounted within said retainer, readily releasable means for retaining said bobbin case within said retainer, said bobbin case and retainer being adapted to enable axial movement of the bobbin case into and out of .the retainer, said bobbin case and retainer having aligned openings in their walls providing a passageway through which a needle may be passed into the interior of the case, and means carried by said bobbin case inwardly of the path of reciprocation of said needle providing a plow-like action across said passageway as the case is removed from the retainer.

3. In a rotary hook of the character set forth in claim 2, said bobbin case having a completely closed cylindrical wall section from the region of said projection to the inner end of said case.

4. In a lockstitch sewing machine of the character set forth in claim 1, said means extending outwardly from said bobbin case having a sloping surface adapted to c0- operate with said needle when the latter is out of proper alignment with said loop seizing member and urge the needle into such proper alignment.

5. In a lockstitch sewing machine of the character set forth in claim 1, said means for retaining said bobbin case retainer against rotation comprising a horizontally extending bar which passes across the outer face of said bobbin retainer, said bar being cut away on its under surface to provide a clearance for the means extending outwardly from said bobbin case as the latter is withdrawn from and inserted in said bobbin case retainer, and said bar having an inwardly and upwardly extending finger cooperating with shoulders on said bobbin case retainer.

6. In lockstitch sewing machine of the character set forth in claim 1, said bobbin case retainer having a channel in its outer face with a vertically extending inner wall, said means for retaining said bobbin case retainer against rotation comprising a finger extending into said channel, and said bobbin case retainer having an axially extending recess therein below said channel arranged to receive snugly said means extending outwardly from said bobbin case.

, 7. In a rotary hook of the character set forth in claim 2, said bobbin case retainer having a recess in the outer face thereof adapted to receive said means carried by said bobbin case, said recess and said means carried by said bobbin case having a cross sectional configuration in a plane perpendicular to the axis lof the rotary hook which adapts said means to shift in a direction parallel with said axis and to be snugly received within said recess.

8. In a rotary hook of the character set forth in claim 7, said means and said recess being of substantially rectangular form in a plane perpendicular to and also in a plane parallel with the axis of the rotary hook.

References Cited by the Examiner UNITED STATES PATENTS 1,504,241 8/ 24 Kohmann 112-231 2,746,407 5 5 6 Ayres 112-228 2,977,910 4/ 61 Covert 112-256 3,083,659 4/63 Kuhar 112-228 3,151,589 10/64 Kuhar 112-228 JORDAN FRANKLIN, Primary Examiner.

DAVID I WILLIAMOWSKY, Examiner.

Patent No. 3,199,480 August 10, 1965 John N. Covert et al.

Column 5, line 60, before "rotation" insert for same column 5, line 61,

for "break" read beak Signed and sealed this 15th day of February 1966.

EST W. SWIDER EDWARD J. BRENNER ting Officer Commissioner of Patents 

2. A ROTARY HOOK FOR A LOCKSTITCH MACHINE WHICH COMPRISES A ROTARY COMPONENT MOUNTED ROTATION ABOUT A HORIZONTAL AXIS AND HAVING A LOOP SEIZING BREAK, A RECIPROCATORY NEEDLE FOR PRESENTING A LOOP OF THREAD TO SAID LOOP SEIZING BEAK, A BOBBIN CASE RETAINER WITHIN SAID ROTARY COMPONENT AND ABOUT WHICH SAID COMPONENT IS ROTATED, A BOBBIN CASE MOUNTED WITHIN SAID RETAINER, READILY RELEASABLY MEANS FOR RETAINING SAID BOBBIN CASE WITHIN SAID RETAINER, SAID BOBBIN CASE AND RETAINER BEING ADAPTED TO ENABLE AXIAL MOVEMENT OF THE BOBBIN CASE INTO AND OUT OF THE RETAINER, SAID BOBIN CASE AND RETAINER HAVING ALIGNED OPENINGS IN THEIR WALLS PROVIDING A PASSAGEWAY THROUGH WHICH A NEEDLE MAY BE PASSED INTO THE INTERIOR OF THE CASE, AND MEANS CARREID BY SAID BOBBIN CASE INWARDLY OF THE PATH OF RECIPROCATION OF SAID NEEDLE PROVIDING A PLOW-LIKE ACTION ACROSS SAID PASSAGEWAY AS THE CASE IS REMOVED FROM THE RETAINER. 